Accepted Article This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/mec.14386 This article is protected by copyright. All rights reserved. DR. GWYLIM SEATON BLACKBURN (Orcid ID : 0000-0001-9112-5121) Article type : Original Article Distinct sources of gene flow produce contrasting population genetic dynamics at different range boundaries of a Choristoneura budworm Authors: Gwylim S. Blackburn 1,2,3* , Bryan M. T. Brunet 1 , Kevin Muirhead 1 , Michel Cusson 2 , Catherine Béliveau 2 , Roger C. Levesque 3 , Lisa M. Lumley 1,2 , and Felix A. H. Sperling 1 Affiliations: 1 CW405 Biosciences Centre, Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 2 Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du PEPS, PO Box 10380, Stn. Ste-Foy, Quebec City, Canada G1V 4C7 3 Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada G1V 0A6 *Correspondence: gwylim.blackburn@gmail.com (fax: 418-648-5849) Running title: Gene flow from multiple sources Keywords: divergence-with-gene-flow, genomic cline, introgression, hybrid zone, Choristoneura, spruce budworm Abstract Populations are often exposed to multiple sources of gene flow, but accounts are lacking of the population genetic dynamics that result from these interactions or their effects on local evolution. Using a genomic clines framework applied to 1195 SNPs, we documented genome- wide, locus-specific patterns of introgression between Choristoneura occidentalis biennis spruce budworms and two ecologically divergent relatives, C. o. occidentalis and C. fumiferana, that it interacts with at alternate boundaries of its range. We observe contrasting hybrid indexes between these hybrid zones, no overlap in 'gene flow outliers' (clines showing relatively extreme extents or rates of locus-specific introgression), and variable linkage disequilibrium among those outliers. At the same time, correlated genome-wide rates of introgression between zones suggest the presence of processes common to both boundaries. These findings highlight the contrasting population genetic dynamics that can occur at separate frontiers of a single